Dynamometric jack



Dec. 20, A H MANN l DYNAMOMETRIC JACK Filed Sept. 7, 1945 FIG. 2.

I INVENToR. ALVIN H. MANN.

ATTORNEY.

Patented Dec. 20, 1949 UNI-TED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 2 Claims.

This invention relates to new and useful improvements in jack devices, and more particularly to jack devices of the dynamometric type especially adapted to apply loads to structures and structural members under test.

In numerous industries, and particularly the manufacture of aircraft, it is necessary that the various structures as well as their component members, be subjected to tests to determine, for

example, the deflection, strength and other physical characteristics of the structure under a predetermined load, and thereby ascertain whether or not the structure conforms to the requirements of the specifications.

It has been the practice prior to the present invention either to load the structure with a deadweight load, for example by placing bags of shot having the desired weight on the structure to be tested, or to place the test structure under the desired load by means of mechanical or hydraulic jacks of conventional design.

The use of bags of shot for this purpose is laborious and time consuming since each bag of shot must be carefully weighed and the several bags must be accurately distributed with respect to the test member or structure in order that the load thereof be properly applied and distributed with respect thereto. Furthermore, these bags of shot not infrequently break with the result that the shot becomes scattered over large areas causing additional delay and wastage of labor and time. On the other hand, the use of hydraulic and mechanical jacks of conventional design for this purpose is objectionable because of the lnability to obtain true axial compression loading of the test member or structure that is entirely free of end moments with the result that accurate loading of the member or structure cannot be obtained.

With the foregoing in mind, the principal object of the present invention is to provide a novel dynamometric jack operable to effect true axial compression loading of structures that is entirely free from end moments.

Another object is to provide a dynamometric jack of the type described that requires a minimum amount of time and labor to install and operate.

A further object is to provide a dynamometric jack having the features and characteristics set forth that is of comparatively simplied construction, relativelyinexpensive to manufacture, and highly eliicientand accurate in operation and use. y

These and other objects of the invention, and the various features and details of the construction, operation and use thereof, are hereinafter fully set forth and described with reference to the accompanying drawing, in which:

Fig. 1 is a view in elevation of a dynamometric jack made according to the present invention; and,

Fig. 2 is a sectional view taken on line 2-2, Fig. 1.

A dynamometric jack made according to the present invention comprises a circular base I, upon the upper face of which are complementary semicircular sections 2 and 3, respectively, having suitably formed semispherical recesses therein that cooperate to provide a spherical socket 4 in which is mounted the lower ball end portion 5 of a jack member 6. The ball portion 5 is relatively loosely mounted in the socket 4 so as to be substantially free to rotate therein within the limits defined by the wall portions 'I of the sections 2 and 3 surrounding the jack member 6. The sections 2 and 3 are accurately centered with respectI to each other coaxially of the base I by means of suitable tapered guide pins 8 and the sections are secured to the said base i by bolts 9.

Forming a part of the jack member 6 and extending from the ball portion 5 thereof outwardly of the socket 4 is a spindle portion I0 that terminates at its upper end in an enlarged portion II having horizontally therethrough suitable openings I2, arranged diametrically and at right angles to each other, to receive a bar (not shown) that can be actuated to rotate the jack member 6.

Upwardly of the portion II the jack member 5 terminates in a coaxial screw I3 of substantial length having a diameter smaller than the portion II. Threaded on the screw I3 is a locking ring I4 provided with a knurled or otherwise roughened exterior circumferential surface as indicated at I5. Y

Also threaded upon the jack screw I 3, endwise of the ring I4, is a piston member I6 having an enlarged head II slidably mounted in the chamber portion I8 of a cylinder I9. The cylinder IB is provided with an upper chamber 2li of slightly reduced diameter that provides between said chambers I8 and 20 a shoulder 2| that functions as a stop to limit upward travel of the piston It. Travel of the piston in a downward direction is limited by a ring 22 that functions also to retain the piston against displacement from the cylinder I9.

Positioned coaxially within the cylinder I9 so as to act between the cylinder-head wall 23 and the face of the piston head I1 is a coil spring 251 that operates to oppose movement of the piston inwardly of the cylinder when the jack member B is rotated to advance the piston I6 along its screw I3. The force exerted by the spring 24 when subjected to compression upon actuation of the piston I6 inwardly of the cylinder I9 is marked upon the exterior of the piston IS, as indicated at 25, for various positions of the piston I6 inwardly of the cylinder I9. The calibration markings are interpreted with reference to the lower end face of the cylinder retaining ring 22 and the jacks of the present invention can b'e provided with springs of different strengths and corresponding markings 25 calibrated to meet the load requirements for any particular job.

The cylinder-head wall 23 projects radially beyond the adjacent cylinder wall to provide a ange 25 to which is secured an assembly 21 comprising a flange portion 28 and a coaxially extending tapered spindle `portion 29 that terminates in a spherical ball portion 39. The ball portion 30 is rotatably mounted in a spherical socketeI dened by a pair of complementary semicircular sections 32 and 33, respectively. These sections 32 and 33, and the socket dened thereby are constructed and arranged with respect to one another and the ball 39 therein, substantially as previously described herein with refer-ence to the sections 2 and 3 deiining the socket l5 in which the ball 5 is mounted. The sections 32 and 33 are centered with respect to the axis of a circular top plate Sil by means of tapered guide pins 35. lSections 32 and 33 and plate Bil are secured together by bolts Se.

Assembly 2'! is made separable from the remainder of the jack in order that there can be interposed and connected between the flange 29 and flange 2E suitable spacer columns (not shown) oi various lengths as required to provide a jack structure of sufficient length of span the distance between the floor or other iixed -support and the member to be placed under load by operation of the jack in the described manner.

In operation of the dynamometric jack the device is disposed between a suitable lixed support and the member to be placed under load, ior example, with the base I resting upon such xed support and the top plate 3:1 in contact with the member to be loaded. A bar (not shown) then is inserted into one of the openings i2 of the jack member 6 and the latter is rotated by actuating said bar in the proper direction to rotate the jack member and cause screw I3 to actuate the piston iii inwardly of the cylinder i9 against the force of the spring 2d. Initially, and until the piston i6 has been actuated to compress the spring 24 suiciently, the piston I5 tends to r0- tate with the screw I3, in which event the piston I6 can be restrained against rotation by manually grasping the arm 9'!! projecting therefrom. However, as soon -as the spring 24 is placed under load, the piston I6 ceases to tend to rotate with the screw I3 and the projecting larm El is released. The screw I3 is rotated to actuate the piston inwardly of the cylinder I9 against spring 24 until the latter exerts the desired load as in dicated by reference to markings 2'5 and when the desired load is obtained the jack can be locked in that position by advancing the locking ring I4 along the screw I3 into engagement With the underside of the piston I6.

By reason of the novel construction and arrangement of parts of a dynamometric jack made according to the present invention and comprising the support assemblies provided endwise of the jack and between it and a fixed support and n the member adapted to be placed under load,

such member or structure can be placed under a true axial compression load entirely free from end moments. The present invention provides a dynamometric jack that is operable to provide compression loading of structural members and structures in a true axial direction and entirely free from end moments. The invention also provides a device of the described type that requires a minimum amount of time and labor to install and operate. A dynamometric jack embodying the present invention is of comparatively simplified construction, relatively inexpensive to manufacture, and highly eiiicient and accurate in operation and use.

While a particular embodiment of the present invention has been illustrated and described herein it is not intended that the invention be limited to such disclosure and changes and modiiications can be made therein and thereto within the 'scope of the claims.

The invention described herein may be manuiactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A jack comprising a cylinder having a bore, piston mounted for rotary and axial sliding in said bore, means limiting axial movement of said piston into and out of said cylinder independent of rotation of said piston, a spring in said bore between one end of said piston and one end of said cylinder, a handle on said piston external to said cylinder, a screw adapted to be threaded axially into and out of the other end of said piston, a ball on said one end of said cylinder, a ball on said screw, and sockets on said balls.

2. A jack comprising a cylinder having a bore open at one end and closed at the other end, said bore adjacent the closed end being narrowed to provide a transverse shoulder, a piston having an enlarged head mounted for rotary and axial sliding in said bore with said transverse shoulder limiting axial movement of said piston into said cylinder indep-endently of rotation of said piston, detachable means in the open end of said cylinder of limiting movement of said piston out of said cylinder independently of rotation of said cylinder, a compression spr-ing in said bore between one end of said piston and the closed end of said cylinder, a detachable radiallyextending handle on said piston external to said cylinder, markings on said piston corresponding with the force exerted by said spring at difierent positions of said piston, a screw adapted to be threaded axially into and out of the other end of said piston, a ball on the closed end of said cylinder, a ball on said screw, and sockets on said balls.

ALVIN I-I. MANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Niunber Name Date 806,581 Chase Oct. 14, V18811 1,281,389 Kaupert Oct. 15, 1918 1,322,397 Ball Nov. 18, 1919 1,828,022 Brand Oct. 20, 1931 1,828,913 Toomey Oct. 27, 1931 1,877,367 Seppmann Sept. 13, 1932 1,907,835 Langbein r- YMay 9, '1933 

